1. Technical Field
This invention generally relates to boring equipment. More particularly, the invention relates to a cutting head for use in conjunction with boring machines to bore through a body of soil and simultaneously lay an underground pipe. Specifically, the invention relates to a rock head that is collapsed to reduce its diameter so that it can enter and travel through the bore of a pipe and that automatically expands to the original diameter once it exits the pipe.
2. Background Information
When underground pipes are to be laid, it is necessary to dig a hole through the soil to lay the pipe. This presents little problem if the pipe is to be positioned close the surface and there are no structures in the way. Then all that needs to be done is to dig a trench, put the pipe in place and fill the trench with soil. However, as urban development progresses, there is a growing need to be able to lay pipe quickly and efficiently and without causing damage to surface structures such as roadways. This can be accomplished by using a process known as auger boring. In this procedure, a boring machine is used to form a horizontal hole or passageway through the soil at the appropriate depth. If the terrain to be bored is hilly, the boring machine may be positioned proximate a hillside. If the terrain is flat, then an excavation pit is dug into the terrain to position the boring machine at an appropriate depth beneath the surface. In either instance, the boring machine is mounted on tracks so that it is able to slide toward and away from the surface into which the hole is being bored. Once the boring machine is in position, a flighted-auger is operationally connected to the boring machine and an appropriate cutting head is attached to the auger. The cutting head is placed into contact with the soil-face and the auger and cutting head are rotated by the boring machine so that the cutting head bores into the soil-face. As the cutting head cuts through the soil, the auger flights direct the excavated material away from the cutting head, out of the hole and to a location proximate the boring machine. Appropriate means are used to move the excavated soil out of the vicinity of the boring machine. Additional sections of auger are added as needed by sliding the boring machine away from the hole, positioning a new auger section rearwardly of the first auger section using a crane, and then securing the auger sections together. The boring machine is advanced forwardly along the tracks toward the soil-face until the next auger section is needed, and then another auger section is attached thereto. This procedure is repeated until the desired length of hole is cut through the soil.
In order to lay the pipe at the same time as the hole or passageway is excavated. In this instance, each section of auger is inserted into a length of pipe before it is lowered into place in front of the boring machine. The cutting head is then attached to the lead auger section. The cutting head needs to have a diameter that is slightly larger than the outside diameter of the pipe being laid, so that the bored hole is large enough to receive the pipe therethrough. The boring machine then advances both the pipe and auger as the cutting head cuts through the soil. The machine pushes the pipe through the soil, but rotates the auger within the pipe. Subsequent sections of auger and pipe are connected as needed. The sections of auger are connected together using the male and female hex connectors they are provided with. The sections of pipe are secured together by welding.
The cutting head selected for boring operations is dependent upon the type of substrate that is being drilled through. If the substrate is generally soil with small stones interspersed therethrough, then the type of cutting head used is known as a dirt head. Dirt heads cut easily and efficiently through soil. Sometimes, however, during boring operations, the dirt head will strike a large rock or a layer of rock. Dirt heads are ill equipped to cut through rock. In the past, if such an obstacle was encountered, then the first thing that was done was that a hole was dug down from the surface in an attempt to intercept and remove the rock, if possible. If, on the other hand, the rock was found to be too large, then the operators would use the dug hole to gain access to the dirt head, remove it from the front of the auger and replace it with a rock head. Rock heads are specially designed to cut through rock, but are fair less efficient at cutting through soil. Consequently, when the harder obstacle had been bored through, the operators would again have to dig down from the surface and replace the rock head with the dirt head.
If the hole was at too great a depth, then an alternative method of swapping the dirt head and rock head would be for the operators to withdraw the auger, pipe and dirt head from within the bored hole, cut the welds in the pipe as needed and disconnect the auger flights from each other. Then when everything was removed from the hole, the rock head would be attached to the lead auger, the auger would be repositioned in the hole and the boring machine would advance the auger and rock head through the hole until the rock or boulder was reached. The rock head would then be used to drill through the rock, then the auger and rock head would be withdrawn from the hole, the rock head removed, the lead auger repositioned within a pipe section and then the dirt head would be reattached to the lead auger. The dirt head and lead auger would then reinserted into the hole and boring would resume. All of this procedure took a considerable amount of time and effort depending on the length of hole and pipe involved. The time period for this type of exchange could extend to days. Alternatively, if the pipe was large enough, then the operator would simply withdraw the auger and dirt head and send a man with a hammer and chisel down the pipe to chip away at the rock involved. All of these methods of removing or boring through the rock would cost a lot of time, money, and effort and would slow the progress of the boring operation to a considerable extent.
There is therefore a need in the art for a rock head that can be quickly and easily attached to the front of an auger during boring operations that occur some depth from the surface without requiring tunneling down from the surface or removal of already installed sections of pipe and auger.